Sheet transfer devices for the reciprocating table of a printing machine



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United States, Patent() i v2,893,732 SHEET TRANSFER DEVICES FORTHE RECIPRO- CATING TABLE OFA PRINTING Wilhelm Christian Hauck, Mannheim, Germany Application July 23,. 1957,; Serial No. 673,738 Claims priority,. application Germany` July 31 1956 1 claims.. (ci. z11-s4) 'Phe present inventionA concerns a sheet transfer device for the reciprocating table of a printing machine. By means of the invention, there is to. be attained a sheet transfer in `an'absolutely stationary condition in order to take over the Valignment effected on the sheet' feeding device appropriately on the printing table, despite .the latter continuing its reciprocating movement' in space and stoppin'g'only at its reversing pointd during an extremely short period.

Thisis attained in that thefront edge of the table, seen in the' direction of printing, is adapted as a separate beading. The beading is xed on a support mountedon the table, said support being subjected to the action of a spring force andI resting onv a'lateral' shoulder and towardsV the return movement end there is associated with the spring torce` atfleast one tappet andJ stops mounted on the machine frame and lying in the orbit of the springforce, bymeans of which the latter can be counteracted in such a manner. that in the region of the abutment thereof the beading stops inspace in the region of. the table reversing movement.

An especially remarkable advantage of the invention consists in the fact that when using suction for retaining the sheets in the separate beading only'a small volume of- 'air needs to be' lcontrolled thus not causing any time delays herewith:

In particular, the invention concerns the sheet transfer device for the printing table of'a screen printing machine, the edgev of which,` located atl right angles to the direction of movement, describes a movement' in space corresponding to a revolving band and in the upper running position issituated atL the front;v This edge is adapted as a1 separate:beadingand'ris fixed.' on a support mounted on the table. The support issubjectedto the force of a spring and'rests' on a` lower anda lateral shoulder. Associated with each spring downwardly and, in the direction of the movement there is a ram, in the course of which there are located stops or guide rails xed on the machine frame, by means of which the spring force can be counteracted that in its abutment region the beading, during the upwards movement of the table from its lower return run, stops in space. For the sheet to be already lying against the beading before the commencement of the linear advance movement of the table, it is necessary for the beading to be already stationary in the first half of the upwards movement of the table. For this purpose, according to the invention, it is necessary to guide the return movement of the table. As the beading, during the return movement, is located at the rear edge of the table, the guide rails according to the invention for the stroke movement of the beading are located opposite the table according to the path in front of the stops for retaining the beading. The beading thus is raised relative to the table and can therefore be pulled by means of the spring acting in the direction of movement above the surface of the table in the direction of movement. When the table commences to carry out its tion by means of the stop of the machine frame acting 2,893,132 atented July 7, V1959 vCf:

upward movement the beading is retained Vin this posi tion by means of the stop of themachine frame acting in the direction'of movement andthe table is pulled forward in van upwards direction over the ledge. Therefore the supporting -shoulders are adapted to Vthe radius of the revolving belt. Sliding the sheet on to the beading in its position lying above the level of the table, is facilitated and ensured by means of thin exible bridging tongues extending to the table. p

Between the described sheet delivery device and the front stops of a sheet -feed apparatus there is .provided moreover, in accordance with the invention a pairk of gripper belts. These grippers convey the sheettowards the movement of the table and areheld under spring action displaceable on a belt carriage in both directions of movement, in the path of which are retaining stops adjustably mountedon the machine frame, so that Vin their region of abutment the grippers during the end movement of the belt carriage remain stationary in space.

With this a gripper movement is shunted from the eX- isting table movement means and despite this there is obtaineda suicient temporary resting period for a gauge reception of the sheet from the feed device and transfer to the beading at the edge of the table. The relative displacement occurring herewithvof the gripper within the belt carriage can be utilized for guiding the gripper along a controlcurve rail provided inthe belt carriage for its opening and closing movement.

The invention will be described further by way of example with reference to' the-accompanying` drawings, in. which:

Fig. 1 is` a perspective. viewof the overall deviceof the instant invention;

Fig. 2 comprisesA sixv diagrams. each showing different positions of thefessentialparts of the apparatus while omitting all other parts; and

Fig. 3 is a diagrammatic detail of the belt carriage gripper.

The screenV frame with the screenl is reciproca-ted in a horizontal. plane. This movement is. imparted thereto by engaging thetable 3 by meansV of slide pins 2. Thev two edges of the table are so connected at right angles to the direction of movement thereof by means' of e11- gaging members or dogs 4 to a separate revolving belt 5 that its plane constantly' describes a plano-parallel path of vmovement in space.r For simpliiication, the'drawing only shows one. dog 4- and only one belt 5.v When printing, the. tablefS ismoved from=left to right atw screen level. It is lowered at the right hand reversing end (Fig. 2, II) and returns in the lower course or path towards the left hand (Fig. 2, III, lV, V), in order to be raised again to the screen at the left hand end (Fig. 2, VI). In the meantime the screen in its linear parallel course in the plane thereof has also returned to the left hand end.

At each side of the screen frame the lower portion of the belt 7 is connected with the frame of the screen by means of a dog 8 reciprocated only on one plane and guided around two turning rollers 6. A belt carriage 9 is engaged in the upper portion of this belt and thus always moves in the opposite direction to the screen 1. A gripper 10 displaceable longitudinally in the direction of movement is mounted on either side in the belt carriage 9 by a spring assembly 11. This gripper travels from the front gauge of a sheet feeding device 12 up to the ledge or beading 13 orf the table, which meets same. Shortly before the point of reversal of the belt carriage 9, the shoulder 14 of the gripper strikes a retaining stop 15 adjustabrly mounted on the machine frame, thus causing the gripper to stop in the belt carriage. As indicated particularly in Fig. 3, the control cam rail 16 which continues to be moved by the belt carriage thus p table edge.

slides along the gripper and opens the same. The front Vof (Fig. 2, V).

'Ihe beading or ledge 13 is provided with suction openings 16' distributed over its entire surface, the vacuum of which is controlled. It is fixed on a support 17 which is adapted to be moved up and is down in a guide 18 and subjected to the action of a spring 19. Spring 19 is accommodated by a shoulder of the table 3 situated under the beading 13. The guide 18 is mounted on a rod 20, which is mounted horizontally in a sliding guide 21. Guide 21 is fixed on the lower surface of the table. The rod 20 is drawn by the force of a compression spring 22 to the left against the table, so that the ledge 13 comes to a stop against a shoulder on the front end of the The rod 20 has a ram end 23 and the support 17 has a ram end 24.

Both ram ends are freely suspended in space during the printing phase I, and also in the right hand reversing position II. During the course of the lower return movement of the table, the ram 24 runs on a guide rail 25 (III). The beading 13 is raised relative to the table and by the force of the spring 22 is `advanced in the direction of return travel. The beading: 13 is supported against the segmental shoulders 26 of the table, a number of which is spread over the length of the edge. The

`beading 13 is lifted up to the plane of the grippers 10,

thus causing the sheets brought thereby to be disposed closely above the beading. Thin exible bridging tongues 27 extended to the table ensure that even if its front edge were to sag the sheet would arrive without mishap on the beading 13.

Fig. 2 position V shows the position in which the ram 23 strikes the retaining stop 28 of the machine frame, so that with continued return movement of the table the beading 13 cornes to a stop in space. At this instant also the gripper has arrived at this point along with the -front edge of the sheet. It then comes to a stop, opens, and allows the sheet to drop on to the beading 13 due to the suction draught from the holes 16 therein, which are located immediately below same. The table 3 itself subsequently moves on the inclined track of the reversing point of the endless belt, until at the end of this movement (Fig. 2, VI), its surface is flush again with the beading 13. The suction apertures distributed over the surface of the table are now also supplied with vacuum, thus causing the complete sheet to rest firmly on the table.- Subsequently the table engagesthe sheet and carries it into the upper path, in which printing is carried out at the screen carried along therewith underneath the fixed doctor. The grippers 10 return to the sheet feeding device and collect a new sheet. The sheet which has just been printed is slid out into the delivery device travelling in front of the sheet to be printed, by means of guide belts.

What I claim is:

1. A sheet transfer apparatus for a printing machine comprising a reciprocating table means having an edge which faces the direction of printing, and including a movable sheet-engaging ledge, spring means normally biasing said ledge in a retracted lower position, and ram and stop means operative during the time said table means is being moved toward a sheet-receiving position for overcoming the action of said spring means, whereby said ledge can be raised relative to said table means so that the sheet previously deposited thereon may be released from said table means and a new sheet fed to said table means.

2. A sheet transfer apparatus as set forth in claim 1 wherein the movement of said sheet-engaging ledge simulates that of an endless belt and wherein the ledge remains substantially stationary in space at the moment the table means is reversed and begins its movement away from a sheet-receiving position.

3. A sheet transfer apparatus as set forth in claim 2 wherein said ledge is provided with thin resilient bridging tongues.

4. An apparatus as set forth in claim 1 wherein said ledge is provided with suction openings connected to a suction drawing means.

5. A sheet transfer apparatus as set forth in claim 2, including means for feeding a sheet to said table means, said feeding means including a pair of grippers, said grippers being adapted to advance the sheet in the direction of the table movement and to deposit the leading edge of the sheet on the sheet-engaging ledge of the table means when said ledge is in a raised position.

6. A sheet transfer apparatus as set forth in claim 5, including means for spring biasing said grippers and means for overcoming the action of said llast mentioned spring biasing means as the grippers reach the sheetengaging ledge on said table means.

7. A sheet transfer apparatus as set forth in claim 3 wherein the ledge is provided with suction openings connected to a suction drawing means.

References Cited in the file of this patent UNITED STATES PATENTS 1,538,184 Hale May 19, 1925 

